Integrated circuits may be formed using various photolithographic techniques. Such techniques typically include use of a Chemical Mechanical Polishing (CMP) process. The CMP process is typically used to grind down and smooth the surface of a semiconductor substrate. In some cases, the CMP process is used to remove some or all of previously formed layer(s) that are no longer needed. For example, trenches may be formed into a semiconductor substrate. Various other layers of material may be deposited within the trenches. To simplify the deposition process, these layers are deposited on the entire semiconductor substrate, including the trench areas and non-trench areas. To remove the deposited layers from the non-trench areas, the CMP process may be applied to grind away the deposited layers.
The CMP process uses a slurry solution that includes a chemical solution with a specific viscosity that will hold very small particles. The particles are made of a hard material such as silica (SiO2) or alumina (Al2O3). These particles help grind away and smooth the surface of the substrate. Conventional CMP processes are designed such that the primary mode of grinding is the mechanical aspect, particularly, the particles. The smaller aspect of the process is the chemical process, which involves a chemical reaction to help remove the surface of the substrate. Such CMP processes work well for planarizing harder materials such as the dielectric material of an interlayer dielectric (ILD).
In some cases, it may be desirable to perform a CMP process on a softer material such as a photoresist material or an anti-reflective coating material. Such materials are typically formed by applying the material as a fluid and hardening that fluid through a baking process. But, the CMP process is generally not designed to work effectively on such materials. Particularly, there may be undesired scratching and peeling. Accordingly, it is desirable to have a CMP process that works effectively on softer materials such as hardened fluid materials.